An illumination optical unit including a transmission optical unit and an illumination-predetermining facet mirror, disposed downstream thereof, is known from WO 2010/099807 A1 and US 2006/0132747 A1. Illumination optical units, in which the illumination-predetermining facet mirror or a corresponding refractive component is arranged in a pupil plane, are known from WO 2005/015314 A2, U.S. Pat. No. 5,963,305 and U.S. Pat. No. 7,095,560. US 2013/0128251 A1 has disclosed a projection exposure apparatus with an anamorphic projection optical unit. DE 10 2011 113 521 A1 discloses a microlithographic projection exposure apparatus. DE 10 2008 009 600 A1 discloses a facet mirror for use in a microlithographic projection exposure apparatus and a projection exposure apparatus equipped therewith. DE 199 31 848 A1 discloses astigmatic components for reducing a honeycomb aspect ratio in EUV illumination systems.